1. Field of the Invention
This invention relates to a novel catalytic hydrodewaxing process utilizing an acidic crystalline zeolitic material of a special group such as ZSM-5 which has had its properties enhanced by controlling its alpha activity to a certain specified range prior to its use in hydrodewaxing operations.
2. Description of the Prior Art
Hydrocarbon conversion processes utilizing crystalline aluminosilicate zeolites have been the subject of extensive investigation as is obvious in both the patent and scientific literature. Catalytic hydrodewaxing operations utilizing ZSM-5 type zeolites are also known in the art and it is also generally known that the performance of these zeolites will be enhanced by treatment of the same with steam. In this connection, U.S. Pat. No. 3,700,585 discloses and claims a hydrodewaxing operation utilizing ZSM-5 type zeolites and at column 8, lines 6 and following, points out that catalysts of improved selectivity and having other beneficial properties in some hydrocarbon conversion processes, such as catalytic cracking are obtained by subjecting the zeolite to treatment with steam at elevated temperatures ranging from about 800.degree. F. to 1500.degree. F. and preferably 1000.degree. F. and 1400.degree. F. This patent does not contain any specific examples of steaming a ZSM-5 type zeolite and the subsequent use thereof in hydrodewaxing operations.
U.S. Pat. No. 4,053,532 is directed towards a hydrodewaxing operation involving a Fischer-Tropsch synthesis product utilizing ZSM-5 type zeolites. However, at column 11, lines 20 and following, it is disclosed that a further improvement can be realized in the Fischer-Tropsch operation or in hydrodewaxing a heavy gas oil stream with a ZSM-5 class of crystalline zeolites with respect to catalyst aging rate if the catalyst is preconditioned with a hydrogen/steam mixture.
U.S. Pat. No. 3,755,145 is directed towards lube oil hydrocracking with ZSM-5 type zeolites utilizing a mixture of ZSM-5 containing a hydrogenation component and another zeolite. This patent discloses at column 5, that steaming of the catalyst mixture is beneficial.
U.S. Pat. No. 3,956,102 is concerned with a process involving the hydrodewaxing of petroleum distillates utilizing a ZSM-5 -type zeolite catalyst. This patent does not contain any specific disclosure of steaming of ZSM-5 type zeolites but it does refer to previously mentioned U.S. Pat. No. 3,700,585 at column 1, lines 66 and following.